Satellite digital audio radio services (SDARS) have become increasingly popular, offering digital radio services covering large geographic areas, such as North America. These services receive uplinked programming, which, in turn, is rebroadcast directly to digital radios that subscribe to the service. Each subscriber to the service generally possesses a digital radio having a receiver and antenna for receiving the digital broadcast. Although many digital radios have been designed for use in vehicles, other digital radios are increasingly being designed for use in the home or office environment, and for personal portable or wearable usage, including in outdoor environments.
In SDARS systems, the digital satellite receivers are generally programmed to receive and decode digital satellite signals, which typically include many channels of digital audio. These signals are received directly from satellites, or from terrestrial repeaters that retransmit the digital satellite signals in order to provide improved coverage and availability. In addition to broadcasting encoded digital quality audio signals, the satellite service may also transmit data that may be used for various other applications. The broadcast signals may include advertising, information about warranty issues, information about the broadcast audio programs, and news, sports, and entertainment programming. Thus, the digital broadcasts may be employed for any of a number of satellite audio radio, satellite television, satellite Internet, and various other consumer services.
In order for a subscriber to receive digital satellite content via a digital radio, the receiver section of the digital radio typically must be able to receive the digital satellite signal from a satellite or terrestrial repeater. In most geographic areas, a clear uninterrupted view of the sky, or proximity to a terrestrial repeater, is generally required in order to properly receive the digital satellite signal. This can be problematic in situations in which a user wishes to use a portable digital satellite receiver while located inside a structure, such as a building or vehicle, or when the user is unable to locate the receiver such that the receiver can receive a digital satellite signal from a satellite or terrestrial repeater.
To provide improved access to digital satellite signals from satellites and/or terrestrial repeaters, some portable digital satellite receivers can be configured to employ multiple antennas. In some implementations, the receiver has an internal antenna, and is configured to allow an additional external antenna to be attached via an antenna jack. Typically, attaching an external antenna to an external antenna jack serves to disable the internal antenna, such that the tuner circuitry in the receiver only receives a signal from the external antenna when an external antenna is attached. If the external antenna is removed, the internal antenna is enabled, and the tuner circuitry in the receiver only receives a signal from the internal antenna. In other implementations, the digital satellite receiver may have two internal antennas built into the receiver. A user switch may then be employed to allow the user to select which of the two internal antennas will be the source of the signal supplied to the tuner circuitry. Although additional antennas (internal and/or external) can provide enhanced reception, these antennas still typically require a relatively clear, uninterrupted reception path between the antenna and the satellite or terrestrial repeater, and therefore do not completely solve the problem of poor reception in structures or vehicles.
One possible solution to this problem is the Delphi XM® Signal Repeater, commercially available from Delphi, which receives satellite signals in a satellite-band from an antenna in or on a structure, such as a house, converts the satellite-band signals to a frequency in the Industrial, Scientific, and Medical (ISM) frequency band, and wirelessly retransmits the converted digital satellite signals in the ISM-band to a repeater antenna module connected to an external antenna jack of a digital satellite receiver located in the structure. The repeater antenna module converts the ISM-band satellite signals back to satellite-band satellite signals, and provides the satellite-band satellite signals to the digital satellite receiver via the receiver antenna input. At this point, the digital satellite receiver processes the satellite-band satellite signals as it would any standard satellite-band satellite signal received directly from a satellite or terrestrial repeater. By using this system, a user can effectively extend the reach of an antenna located in or on a structure to other digital receivers in the structure.
FIG. 1 generally illustrates a conventional portable digital satellite receiver 10 employing multiple antennas and configured to switch among the multiple antennas. Portable digital satellite receiver 10 includes an internal digital satellite antenna 11 configured to receive a digital satellite signal in a digital satellite frequency band, such as 2.3 GHz. Antenna 11 provides an amplified digital satellite radio signal to an antenna switch 26. Portable receiver 10 is also shown having a connector 23 coupled to antenna switch 26. Connector 23 is configured to receive a connector from an external antenna and to provide an electrical connection between an external antenna and antenna switch 26.
One example of an antenna that can be removably coupled to connector 23 to provide an antenna signal to portable receiver 10 is an external SDARS antenna 13 configured to receive a digital satellite radio signal at approximately 2.3 GHz, and to provide an amplified version of that signal as an output. External SDARS antenna 13 operates in a manner similar to internal SDARS antenna 11. External repeater antenna 39 is another example of an antenna that can be removably coupled to connector 23. External repeater antenna 39 receives a signal in an Industrial, Scientific, and Medical (ISM) frequency band, converts the received signal in the ISM-band to a digital satellite signal in a digital satellite frequency band at approximately 2.3 GHz, and provides it as an output. As shown, either external SDARS antenna 13, or external repeater antenna 39, or no external antenna may be removably coupled to connector 23.
Antenna switch 26 provides an input signal to tuner 29 of receiver circuitry 28. The signal provided to tuner 29 by antenna switch 26 is determined based on whether or not an external antenna 13 or 39 is removably coupled to connector 23. If no external antenna is removably coupled to connector 23, antenna switch 26 provides the digital satellite signal received by internal SDARS antenna 11 to tuner 29. If an external antenna is coupled to connector 23, antenna switch 26 disables internal SDARS antenna 11, and provides a digital satellite radio signal provided by the external antenna coupled to tuner 29. Tuner 29 down-converts the received 2.3 GHz signal received from the antenna selected by antenna switch 26 to a baseband signal, also known as a ZIF, or zero-IF (zero intermediate frequency) signal. The ZIF or baseband signal output by tuner 30 is an analog signal containing I (in-phase) and Q (quadrature) signal information. The receive chipset 31 receives the analog ZIF or baseband signal from tuner 29, digitizes the analog signal and extracts audio and/or other data. The extracted audio and/or other data is then further processed by receiver 28 resulting in audio and/or data output.
Because tuner 29 is only configured to process a signal from one antenna selected by antenna switch 26 at any given time, a loss of data generally may occur when antenna switch 26 switches from an internal antenna 11 to an external antenna 13 or 39, or vice versa. A loss of signal can also occur if, for example, the external repeater antenna 39 is coupled to connector 23, and the user moves to a location without ISM repeater coverage. In addition, for portable receiver 10 to switch between an internal antenna 11 and an external antenna 13 or 39, a user is generally required to physically couple or uncouple an external antenna 13 or 39 to connector 23.
While the provision of multiple antennas, be they digital satellite antennas or repeater antennas, can provide enhanced performance for digital satellite receivers, physically attaching or removing external antennas, and user switching among multiple antennas using switches in conventional approaches, can be inconvenient. In addition, whether the switching is between internal antennas or between an internal antenna and an external antenna, the process of switching between antennas can cause the signal to the receiver tuner circuitry to be interrupted. This interruption, caused by delays due to switching, can lead to an interruption in the audio or data output by the receiver, and a sub-optimal user experience.
What is needed is a digital satellite receiver system that can conveniently switch among multiple antennas while minimizing signal processing delays associated with switching, reducing consequent degradation in audio and/or data output from the receiver.